The present application relates to an NMR logging tool and related methods.
Well logging is a common practice in the oil and gas industry to evaluate underground formations for the presence and producibility of subterranean formations. Among the most important parameters determined in the process are the depth and thickness of formation layers containing hydrocarbon, the formation porosity (i.e., the relative amount of void space in the formation), the hydrocarbon saturation (i.e., the relative percentage of hydrocarbons versus water in the pore space), and the permeability of the formation (i.e., the ability of the oil, gas, or water to flow out of the formation, into the well and eventually to the surface for recovery).
Presently, nuclear magnetic resonance (NMR) logging is considered one of the most effective techniques for determining these geologic parameters. NMR logging utilizes an NMR logging tool coupled to a drill string for analyzing the surrounding formation during a drilling operation.
NMR technology has many advantages over other logging techniques (such as gamma ray logging, sonic logging, electric logging, and others), one of the most significant being the independence of NMR measurements from formation lithology. In particular, NMR data relates in a simple manner to formation pore sizes. This relationship facilitates detection of formation fluids (e.g., gas, oil, and water) independent of the matrix mineralogy. To this end, in addition to estimation of formation porosity, hydrocarbon saturation, and permeability, NMR logging enables computation of clay-bound water, capillary-bound water, and free fluid volumes, which aid in comprehensively evaluating the subterranean formation.